Update:
I updated Amibroker to 6.30.5 and everything worked. On my other machine the old version still worked until twenty minutes ago (a couple of days after the first machine stopped working) and then I got the same error message. I upgraded that machine to 6.30.5 and it works fine.
I have no idea WTF it is that caused this. I seem to remember it happened two years ago and I did the same thing. I wrote to Tomasz but he wants to see a copy of the code….That’s not going to happen It can’t be a code thing and it can’t be an update to Windows as I haven’t done any. Tomasz wouldn’t believe that as he seems to assume everyone is an idiot, which in most cases they are so you can’t blame him.
Anyway if it happens to you, upgrade Amibroker